Apply a Function over a Ragged Array in R Programming – tapply() Function

tapply() function in R Language is used to apply a function over a subset of vectors given by a combination of factors

Syntax: tapply(vector, factor, fun)

Parameters:
vector: Created Vector
factor: Created Factor
fun: Function to be applied

Example 1:

# R Program to apply a function
# over a data object

# Creating Factor
fac <- c(1, 1, 1, 1, 2, 2, 2, 3, 3)

# Created Vector
vec <- c(1, 2, 3, 4, 5, 6, 7, 8, 9)

# Calling tapply() Function
tapply(vec, fac, sum)

Output:

 1  2  3 
10 18 17 

This is how above code works:


Example 2:

# R Program to apply a function
# over a data object

# Creating Factor
fac <- c(1, 1, 1, 1, 2, 2, 2, 3, 3)

# Created Vector
vec <- c(1, 2, 3, 4, 5, 6, 7, 8, 9)

# Calling tapply() Function
tapply(vec, fac, prod)

Output:

 1   2   3 
24 210  72